Local Storage in JavaScript - how to make sure all data is stored in local storage?

//all task information saved in local storage 
//check to see whether local storage supported and available
function storageAvailable(type) {
    var storage;
    try {
        storage = window[type];
        var x = '__storage_test__';
        storage.setItem(x, x);
        storage.removeItem(x);
        return true;
    }
    catch(e) {
        return e instanceof DOMException && (
            // everything except Firefox
            e.code === 22 ||
            // Firefox
            e.code === 1014 ||
            // test name field too, because code might not be present
            // everything except Firefox
            e.name === 'QuotaExceededError' ||
            // Firefox
            e.name === 'NS_ERROR_DOM_QUOTA_REACHED') &&
            // acknowledge QuotaExceededError only if there's something already stored
            (storage && storage.length !== 0);
    }
}

//check to see if local storage usable
if (storageAvailable('localStorage')) {
     console.log('Yes! We can use localStorage')
  }
  else {
     console.log('No, no localStorage')
  }

  //check to see if local storage populated
  if(!localStorage.getItem('sort', 'newTask', 'taskDescr', 'startDate', 'category', 'priority')) {
    populateStorage();
    console.log('Storage populated')
  } else {
    empty();
    console.log('Storage not populated')
  }

  //create two data entries in local storage, and then delete them
  function populateStorage() {
    localStorage.setItem('sort', 'A');
    localStorage.setItem('newTask', 'coffee');
    console.log('Data entries in local storage populated')
  
    //localStorage.clear();
    //console.log('Local storage cleared')
  }

  // Check browser support
if (typeof(Storage) !== "undefined") {
  // Store
  localStorage.setItem("sort", "A");
  // Retrieve
  document.getElementById("result").innerHTML = localStorage.getItem("sort");
  console.log("result")
} else {
  document.getElementById("result").innerHTML = "Sorry, your browser does not support Web Storage...";
}